Yes I have taken a scrap caravan from
Ebay stripped it down to the bare chassis and built a coop on it
The standard caravan build of thin plywood with an aluminium outer skin is not really suitable.
Far too weak once the cabinets are removed, not waterproof and a haven for pests.
Most old UK caravans are so rotten there is little worth using on them other than the chassis.
I based my build on this concept but without the huge gas ram doors or the $5000 egg handling system
http://chickencaravan.com/
I used a recycled plasticcalled stokboard for the walls fixed to an external timber frame so the entire interior can be pressure washed and has nowhere for red mites to hide.
I did not use metal because here in the UK it would suffer far too much condensation
For the floor I used 2mx2m kennel panels with 5cm gaps between the bars so the poop fall on the grass.
The caravan is vented top and bottom and most of the sides have windows covered by recycling some of the original caravan windows so they provide light and rain protection but are never completely closed
the perches are all 5M long and can be withdrawn through the rear window for cleaning
The roof is onduline (bitumen) sheeting
The towbar brakes and wheels all work and the structure is strong enough to be towed on the open road if necessary.
The four original jacks plus the jockey wheel can be used to get it reasonably level although that's not crucial
I towed it around my field once a week with a small compact Iseki tractor until early winter however moving anything on clay in the winter is not a nice experience and the grass gets badly damaged
So I built my caravan with a very low roof for a specific reason in the winter I bring it up out of the field and it needed to be low enough able to fit under my carport so the birds have a large dry area on wet days
Post pictures if you do it, that would be super cool 
